Drainage catheters may be used where fluid has collected in the body and requires removal. Examples include the drainage of a hematoma (collection of blood), billoma (collection of bile), or urinoma (collection of urine). Drainage catheters may be used to percutaneously drain an abscess or pocket of fluid in the body to the exterior by means of gravity or negative pressure. Typical abscess fluids include biliary, nephrostomy, pleural, urinary, and mediastinal collection.
Catheterization can be used to drain the bladder after surgery or when the genitourinary system is plugged by an obstruction. Typically, drainage catheters may lie in a patient for a fairly long period of time. Accordingly, catheters have been developed with anchor structures to prevent inadvertent removal of the catheter from a patient. A “pigtail loop” as is disclosed in U.S. Pat. No. 6,231,542, is one such anchor and is formed by a flexible tube portion at the distal end of the catheter. The pigtail loop may be created in the catheter by forming the flexible tube of the catheter of a memory material. A stiff cannula or similar implement may be inserted through the catheter lumen to straighten the pigtail loop for introduction into the patient. The distal end of the flexible tube returns to the pigtail loop configuration after the cannula is removed. Alternatively, the end of the catheter can be flexible and pulled into the pigtail or other anchoring configuration by pulling a tension member, e.g. a suture wire that extends from the distal end of the catheter to and out of the catheter near its proximal end. The suture wire can be attached to draw ports located at two separated positions along the distal portion of the catheter. Pulling the suture juxtaposes the draw ports and forms a pigtail loop at the distal end of the catheter. A physician can secure the pigtail loop by grasping and pulling on one or more suture threads that lead distally from the pigtail loop. When the suture thread is taut, it prevents the pigtail loop from straightening by holding the juxtaposed portions of the catheter together. The catheter tip can be returned to its straight configuration by releasing the tension of the suture at its proximal end.
With some catheters, tying or locking the suture thread prevents the pigtail loop from straightening. However, if the suture thread is loosened or becomes unsecured, the pigtail loop or other anchor at the distal end of the catheter may be released and the catheter inadvertently released and withdrawn from the patient.